donderdag 13 juni 2013

HPA-as, cortisol, hersenfuncties/immuniteit/ontstekingen/bloeddruk/suiker en vetmetabolisme,..

Enkele wetenschappelijke artikels voor mensen die graag wat meer achtergrondinfo hebben.
Soms krijg ik reacties zoals "dan moet gij me eens uitleggen wat emoties te maken hebben met mijn natural-killer-cells" of "hoe kan ik mijn Epstein-Barr / Mononucleose nu genezen door aan mijn emoties te werken, dat is toch absurd ?" Hieronder niet mijn antwoord maar dat van gerenommeerde wetenschappers terzake.

Staufenbiel, S.M., et al., Hair cortisol, stress exposure,.. (a systematic review (2012).

A frequently assessed hormone in psychoneuroendocrine research is cortisol. Cortisol is a glucocorticoid hormone and is released by the adrenal cortex through stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. Cortisol is crucial for proper body and brain functioning as it regulates numerous basal processes such as fat and glucose metabolism, blood pressure, inflammatory and immune responses, and thereby aids the organism to flexibly adjust to environmental challenges. It is also commonly known as the stress hormone because it is released in higher doses under stressful conditions. In the reaction to basically all stressors, two classes of hormones are released; catecholamines and glucocorticoids, and the speed and magnitudes of both parts depend on the specific stressor.

 “I fit goes up, must it come down ? Chronic stress and the Hypothalamic-Pituitary-Adrenocortical Axis in Humans” Gregory E. Miller, Edith Chen, and Eric S. Zhou (psychological bulletin 2007, vol 133, No 1, 25-45)

“Cortisol plays a key role in the central nervous system, where it is involved in learning, memory, and emotion; in the metabolic system, where it regulates glucose storage and utilization; and in the immune system, where it regulates the magnitude and duration of the inflammatory responses and the maturation of lymphocytes. Moreover, these are just the most prominent examples of cortisol’s actions; its influence also extends to multiple other systems in the body.”
“Cortisol is a critical biological intermediary; it is seen as a primary mechanism through which chronic stressors get inside the body to bring about disease. Models of this type have been articulated for psychiatric disorders such as depression and schizophrenia; medical conditions such as cancer, arthritis, and diabetes; and lifestyle problems such as obesity and fatigue.”
“Stress triggers disease by increasing output of cortisol, thereby exposing bodily tissues to elevated concentrations of the hormone. If sustained, this process is thought to lead to tissue damage and subsequent dysregulation of biological systems. In contrast to these models, there also is now a handful of theories positing that stress-induced declines in cortisol output are the culpit mechanism. These models are generally advanced to explain how stress could exacerbate conditions in which deficient cortisol signaling contributes to disease pathogenesis. This may be the case with rheumatoid arthritis, chronic fatigue syndrome, and post traumatic stress disorder (PTSD).”
“The results indicate that exposure to chronic stress is associated with significantly lower concentrations of morning cortisol, and more pronounced suppression of cortisol following dexamethasone challenge. It is also associated with greater concentrations of afternoon/evening cortisol, a flatter diurnal rhythm, and a higher daily volume of cortisol output. Collectively, these findings suggest that chronic stress is accompanied by a dysregulated pattern of hormone secretion, with lower than normal morning output but higher than expected secretion across the rest of the day. This pattern gives rise to a flattened diurnal rhythm. In healthy persons not exposed to chronic stress, cortisol usually displays a robust diurnal rhythm, with values highest in the morning and lowest in the evening."

Brin Behav Immun 2012 oct 26(7);1019-29, doi: 10.1016/j.bbi.2012.02.002. Epub 2012 feb 15
Analysis of cortisol in hair--state of the art and future directions.
Stalder T, Kirschbaum C.
Department of Psychology, Technical University of Dresden, 01069 Dresden, Germany.

Changes to long-term secretion of the glucocorticoid cortisol are considered to play a crucial role in mediating the link between chronic stress and the development of numerous immune system related diseases. However, obtaining valid assessments of long-term cortisol levels is difficult due to limitations of previous measurement strategies in blood, saliva or urine. This review discusses evidence on a recent methodological development assumed to provide a considerable advancement in this respect: the analysis of cortisol in hair. Being incorporated into the growing hair, hair cortisol concentrations (HCC) are assumed to provide a retrospective reflection of integrated cortisol secretion over periods of several months. Over the past years, supportive evidence has accumulated regarding several fundamental characteristics of HCC, including its validity as an index of long-term systemic cortisol levels, its reliability across repeated assessments and its relative robustness to a range of potential confounding influences. Based on this groundwork, research has now also commenced to utilise HCC for answering more specific questions regarding the role of long-term cortisol secretion in different stress and health-related conditions. The possibility of extending hair analysis to also capture long-term secretion of other steroid hormones (e.g., androgens or estrogens) provides a further intriguing prospect for future research. Given its unique characteristics, the use of hair analysis holds great promise to significantly enhance current understanding on the role of steroid hormones in psychoimmunological research